For the most part the forum activity for faction members is optional. We forum users are actually a minority in the server population. A space was provided for them to use this option if they so wish. I know though that when I ran GMG| I was trying to cultivate it as both an in-game and forum faction. I made it so that to simply move up the initial rank (and get access to the beloved Kaichou) an inRP message dump post with evidence of the in-game action is required. They still have this requirement in place and I enjoy reading our message dump reliving the memories.
It's up to the leadership and it's members what to do with the space. It's there if they want to use it but officially it's optional.
Please note that this is also the case with the Faction Feedback threads. It's optional. The space is provided if they wish to use it. Most do.